A sampling gate of this type, particularly designed for the transmission of voice samples in a TDM telephone system operating with pulse-amplitude modulation (PAM) and using resonant transfer (see commonly owned U.S. Pat. No. 3,499,199), may comprise a pair of junction transistors of the same conductivity type (NPN OR PNP) inserted in bucking relationship, with their emitters and their bases directly interconnected, between the live local wire and the hot trunk conductor. An electronic switch constituted by such a transistor pair has been described in an article by K. W. Cattermole, IEEE publication of September 1958, entitled "Efficiency and Reciprocity in Pulse-Amplitude Modulation"; see also a book by the same author entitled "Principles of Pulse-Code Modulation", published 1969 by ILIFFE Books Limited, London. Reference in this connection may further be made to commonly owned Italian Pat. No. 1,014,576 and to the corresponding British Pat. No. 1,501,421 and Canadian Pat. No. 1,067,188.
According to the aforementioned commonly owned patents, the suppression of cross-talk in such a TDM/PAM telephone system is facilitated by the use of a trunk line in the form of a coaxial cable whose conductors have a thickness less than the penetration depth of the alternating signal currents, thereby reducing the intensity of parasitic currents traversing these conductors. Such a coaxial cable is also disclosed in commonly owned U.S. Pat. Nos. 3,878,485 and 3,973,227. I have found, however, that the increased resistance of the coaxial cable due to the small thickness of its conductors results in another source of cross-talk, namely an enhanced leakage current passing through the usually grounded cold conductor of the trunk line and the common power supply serving for the energization of the associated local lines.